Can extended mash circulation lead to excessive lipids and a loss of body? RE: Noonan

So I am reading Noonan's New Lager Brewing, and in the sparging section he states (from memory) that excessive vorlauf (what I read as recirculation) can lead to a major loss of body and a significant increase in unwanted compounds such as lipids.

I have heard of this before, but never in a context with any scientific backup. Now this has me worried that a continuous recirculation during a mash may not be a good way to go. Does anyone have an opinion either way. I would like to get a bit more of the science behind this.

The degree of clarity that should be obtained in the runoff is a matter of debate. A lot of draff carried into the kettle is a recipe for astringent beer, but a small amount may improve trub coagulation. The majority of brewers recycle until the runoff is no longer heavily clouded; this is generally accomplished in less that ten minutes. Excessive recycling may lead to greater lipid levels in the wort and ought to be avoided.

Unless the system is pumped and the wort is being forced through the grain bed I have trouble seeing how recirculation could extract more lipids, if it doesn't mention the same problem occurring from over sparging as well.

Well, let's look at a few things (all paraphrased or quoted from Brewing Science and Practice- Briggs, et al.):

Effects of lipids:
1. In the mash and when combined with other compounds, "can slow down starch gelatinization and impede amylolysis and the degradation of complexed dextrins" (bad).
2. Increases fermentation rate, yeast viability, and tolerance to high alcohol environments (good)
3. Reduce head retention (bad)
4. Indirectly increase esters through yeast metabolism (good or bad depending on beer style)
5. Can lead to faster oxidation in stored beer (bad)

The primary concern, however, seems to be foam stability (head retention).

Here's what can cause increased lipids into wort:
"The amounts of lipid extracted into wort is increased by using better modified malts, finer grinding, higher mashing and sparging temperatures, thinner mash beds during wort separation, careless and excessive raking in the lauter tun, by using smaller proportions of adjuncts, and by running off faster, by `squeezing' the mash to recover residual extract, or by adopting other techniques to maximize extract recovery."

Also of note:
"Much of the lipid in a mash is present as oil droplets spread among the grist particles. In general, more turbid worts carry more lipids and techniques are usually adopted to minimize turbidity and the amounts of lipid remaining in the wort"

It seems to me that lipids are already there and aren't increased by much through any means IN the mash itself (except grind and mash temps, but that's probably pretty minimal). The main concern is in the lauter. So, you can recirculate all you want during the mash as long as you take measures to make the wort going to the boil kettle relatively clear.

OK. So what Noonan is saying is that during Mash out (~170º) if you vorlauf excessively at that high temp, you have a greater likelihood of extracting the lipids that are already present in the mash (or at least a larger concentration of them). So a properly set mash bed should be fine.

Quote:

The amounts of lipid extracted into wort is increased by ... running off faster

Do you think this could be a potential detriment to our fast sparge technique?

I just rented Brew Science and a couple other texts. I am excited to be getting into this more technical side of brewing!

Here's what can cause increased lipids into wort:
"The amounts of lipid extracted into wort is increased by using better modified malts, finer grinding, higher mashing and sparging temperatures, thinner mash beds during wort separation, careless and excessive raking in the lauter tun, by using smaller proportions of adjuncts, and by running off faster, by `squeezing' the mash to recover residual extract, or by adopting other techniques to maximize extract recovery."

The two parts I bolded are what I suspect might be the biggest culprits. In all grains, the vast majority of oils are stored in the embryo, and then as the grain is malted, in the developing acrospire. Therefore anything that would lead to more broken acrospires during the mashing process is more prone to having more oils going into the wort. Or any other procedure that might improve oil extraction.

I personally am a bit skeptical about many of the concerns about oils in wort. Yeast are perfectly able to take up and metabolize oils - as long as it is not excessive. Actually my biggest concern with excessive oils is the potential of their oxidation leading to off flavors. I'm hoping this is fairly temperature sensitive, such that oxygenating cool wort that has extra oils does not lead to much oxidation (as opposed to hot/warm oxygenation). I've got one experiment in the carboy that will shed some light on this and I have another one planned that is an even better test. I'll wait until I get some results before posting any more details.

Do you think this could be a potential detriment to our fast sparge technique?

I think the degree of any negative effects would depend on the details of the MLT design and technique. I think the bottom line is, if your beer has satisfactory foam stability and acceptable flavor-active compound levels (or minimal in the case of lagers), then as long as the wort going into the boil kettle is clear, you should be fine. I'll accept it as a possibility, but not enough to make me change yet... if that were the case, the whole idea of batch sparging would have the same effect.

Quote:

Originally Posted by pjj2ba

Actually my biggest concern with excessive oils is the potential of their oxidation leading to off flavors.

I would also be concerned about ester production in the case of lagers and other clean beers.

I'll accept it as a possibility, but not enough to make me change yet... if that were the case, the whole idea of batch sparging would have the same effect.

Maybe this was the fact that lead BYO to publish that fly-sparging produces a higher quality wort. We had that argument last year sometime, but this never came up. It is an interesting thing to ponder.

In general, I think my fears are abated. I think as long as I recirc at mash temps, properly set my filter bed, and sparge with in range water without over sparging I have nothing to be concerned about.